Porta One - No Sound

[tanner.ledford]

Hello all

Just picked up a Porta One for repair through eBay. The listing described the usual transport issues with these things (playhead not engaging, auto-stopping, rewind stuck, etc etc), all of which I've already fixed. But now I've discovered it has other issues that I can't find any information on. It seems like the entire thing isn't passing any signal at all. None of the mic/line inputs seem to be getting any signal, as the VUs aren't moving. The VUs also aren't responding to any audio from the tape playback. No signal coming out of any of the outputs - headphone out, line out, and all four tape outs. If I really crank my monitors I can hear some dust in the faders when I move them and some popping when I switch the channel input, so I know it's not an issue with the outputs themselves. It's gotta be something internal down the line. Also, the LED under the power button doesn't turn on. Not sure if that indicative of anything. Does anyone have any idea what's going on?

Thanks in advance!

 

[SkywaveTDR]

If the LED does not turn on that would be a sign that the power supply is bad or that some part of it is out and maybe that a wrong supply at one time was plugged in. There is a U501 that manages mute and the LED and that is where you should look for an answer It is a M5232L IC that is listed as a voltage detector alarm circuit that the LED is connected to directly. The Regulator for some parts is a LM7810. The deck appears to have a negative center plug. People often plug in the wrong supply and damage the unit.